Control and Co-ordination
EXERCISE
Multiple choice question.
1.The nervous system of mammals uses both electrical
and chemical means to send signals via neurons. Which part of the neuron
receives impulse?
1.
Axon
2. Dendron
3.
Nodes of Ranvier
4.
Neurilemma
2.___________ is a neurotransmitter.
1.
ADH
2.
Acetyl CoA
4.
Inositol
1.
Oligodendrocytes
2.
Satellite cells
3.
Astrocytes
1. Tract
2.
Nucleus
3.
Nerve
4. Ganglionl
1.
in cytoplasm
2. on cell surface
3.
in nucleus
4. on
Golgi complex
6.If
the parathyroid gland of man is removed, the specific result will be
___________.
1.
onset of aging
2. disturbance of Ca++
3.
onset of myxoedema
4.
elevation of blood pressure
1.
Glycine
2.
Arginine
3.
Ornithine
4. Tyrosine
1.
skin colour
2.
excretion
3.
digestion
4. behaviour
1.
Salivary, thyroid, adrenal, ovary
2.
Adrenal, testis, ovary, liver
3. Pituitary, thyroid, adrenal, thymus
4.
pituitary, pancreas, adrenal, thymus
2.
Corpus albicans
3. Corpus
spongiosum
4. Corpus
callosum
Solution:
After ovulation,
the Graafian follicle changes into Corpus luteum.
1.
Parathyroid hormone - Diabetes insipidus
2.
Leutinising hormone - Diabetes mellitus
3. Insulin - Hyperglycemia
4. Thyroxine
- Tetany
12.___________ is in direct contact of brain in human.
1.
Cranium
2.
Duramater
3.
Arachnoid
4. Piamater
1.What
is the function of the red nucleus?
ans: Near the centre of the midbrain
is a mass of grey matter scattered within the white matter. It is called the
red nucleus. It plays an important role in controlling posture and muscle tone,
modifying some motor activities, and motor coordination.
2.What is the importance of Corpora quadrigemina?
Solution:
Cerebellum: It
is the second-largest part of the brain and consists of two lateral hemispheres
and a central vermis. It is composed of white matter with a thin layer of grey
matter, the cortex. The white matter intermixes with the grey matter and shows
a tree-like pattern called arborvitae. The surface of the cerebellum shows
convolutions (gyri and sulci) a number of nuclei lie deep within each lateral
or cerebellar hemisphere. Over 30 million neurons lie in the cortex. Three
pairs of myelinated nerve bundles called cerebullar penduncles to connect the
cerebellum to the other parts of the CNS.
Functions: It is an important centre that
maintains the equilibrium of body, posture, balancing orientation, moderation
of voluntary movements, maintenance of muscle tone. It is a regulatory center
for neuromuscular activities and controls rapid activities like walking,
running, speaking, etc. All activities of the cerebellum are involuntary
(though may involve learning in early stages).
4.Name the three ossicles of the middle ear.
Solution:
Middle ear: It
consists of a chain of three ear ossicles called Malleus (hammer), Incus
(anvil), and Stapes (stirrup-the smallest bone). On receiving the vibrations
from the tympanic membrane, the ear ossicles amplify the vibrations and transfer
these to the cochlea.
A short
Eustachian tube connects the middle ear to the pharynx. It equalizes air
pressure on both sides of the eardrum.
5.Name
the hormone which is an anti-abortion hormone.
Solution:
Progesterone
Solution:
Placenta
Solution:
Steroids
Solution:
Excessive
secretion of Growth Hormone causes abnormal elongation of long bones of arms
and legs and of the lower jaw.
Solution:
Melatonin
Solution:
Thymus gland
Short
answer question
1.Describe the endocrine role of islets
of Langerhans.
Solution:
Islets of Langerhans
are endocrine cells of the pancreas. They are four types of cells in Islets of
Langerhans which have an endocrine role i.e. they secrete hormones.
i.
Alpha cells (α cells): They constitute 20% of Islets of
Langerhans. They secrete hormone glucagon. Glucagon stimulates glycogenolysis
(the breakdown of glycogen) in the liver which causes hyperglycemia.
ii.
Beta cells (β cells): They constitute 70% of Islets of
Langerhans. They secrete insulin which stimulates glycogenesis (formation of glycogen)
in the liver and muscles. Insulin causes hypoglycemia by increasing the uptake
of glucose by cells.
iii.
Delta cells (δ cells): They constitute 10% of Islets of
Langerhans. These cells secrete somatostatin which inhibits the secretion of
insulin and glucagon. It also lowers gastric secretions, motility, and
absorption in the digestive tract. Somatostatin inhibits the release of growth
hormone.
iv.
PP cells or F cells: These cells secrete pancreatic polypeptide (PP) and inhibit the
release of pancreatic juice.
2.Mention the
function of testosterone?
Solution:
The group of hormones
secreted by testis is androgens such as testosterone.
Functions
of androgens:
i. It is also
responsible for the appearance of secondary sexual characters such as facial
and pubic hair, deepening of the voice, broadening of shoulders, male
aggressiveness, etc.
ii. It involves in
development of testis.
3.Give symptoms of the disease caused by hyposecretion of ADH.
Solution:
This condition causes
excessive micturition or polyuria, polydipsia (increased thirst), etc.
Solution:
i. When Rakesh fell
down from his motorbike the inner membranes called meninges protected his brain
from injury.
ii. These meninges
form a protective covering around the brain and spinal cord. They act as shock
absorbers.
Solution:
The medulla oblongata
is a part of the brain stem.
iii. It also controls
non-vital reflex activities like coughing, sneezing, swallowing, vomiting,
yawning, etc.
iv. Thus, damage or
injury to medulla oblongata may disrupt these vital functions. Therefore,
injury to medulla oblongata may prove fatal.
Solution:
i.
Heart: Sympathetic nervous system accelerates the heartbeat whereas the
parasympathetic nervous system decelerates the heartbeat.
ii.
Urinary bladder: Sympathetic nervous system inhibits bladder contraction whereas
the parasympathetic nervous system stimulates bladder contraction.
Solution:
i. Mr. Kothari may be
suffering from Graves’ disease.
ii. It is caused due
to increased levels of thyroid hormone or hyperthyroidism.
Solution:
i. Excitability/Irritability:
Nerve fibres have polarized membranes, thus they have the ability to
perceive stimulus and enter into a state of activity.
ii. Conductivity:
It is the ability of the nerve to transmit impulses along the whole length of
the axon.
iii. Stimulus:
It is any detectable, physical, chemical, electrical change in the external or
internal environment which brings about excitation in a
nerve/muscle/organ/organism. A
stimulus
must have a minimum intensity called threshold stimulus, in order to be
effective. The subliminal (weak) stimulus will have no effect while the
supraliminal (strong) stimulus will produce the same degree of impulse as the
threshold stimulus.
iv. Summation
effect: A single subliminal stimulus will have no effect but when many such
weak stimuli are given again and again they may produce an impulse due to
summation of effects.
v. All or none law:
The nerve will either conduct the impulse along its entire length or will not conduct
the impulse at all. This occurs in the case of a subliminal or weak stimulus.
vi. Refractory
period: It is the time interval (about a millisecond) during which a nerve
fails to respond to a second stimulus even if it is strong.
vii. Synaptic
delay: The impulse takes about 0.3 to 0.5 milliseconds to cross a synapse.
It is required for the release of neurotransmitters from the axon terminal and
excitation in the dendron of the next neuron.
viii. Synaptic
fatigue: The transmission of nerve impulses across the synapse stops
temporarily due to the depletion of the neurotransmitter.
ix. Velocity:
The rate of transmission of impulse is higher in long and thick nerves. It is
higher in homeotherms than in poikilotherms. The velocity of transmission is
higher in voluntary fibres (100 - 120 m/s in man) as compared to autonomic or
involuntary nerves (10-20 m/s). In medullated nerve fibre, the velocity of
transmission is higher as an impulse has to jump from one node of Ranvier to
the next.
9.How does the tongue detect the
sensation of taste?
Solution:
The tongue detects
the sensation of taste due to gustatoreceptors.
Solution:
i.
Site of production: Secretin, gastrin, and cholecystokinin are secreted in the
gastrointestinal tract
ii.
Functions:
Secretin:
It is responsible for the secretion of pancreatic juice from the
pancreas and bile from the liver.
Gastrin:
It stimulates gastric glands to produce gastric juice.
Cholecystokin
in CCK/ Pancreozymin PZ: It stimulates the pancreas to release
enzymes and also stimulates the gall bladder to release bile.
Solution:
i. The patient may be
suffering from myxoedema.
ii. It is caused due
to the deficiency of thyroid hormones (hypothyroidism) in adults.
iii. Care: Patients
should take prescribed medications regularly and eat food rich in iodine.
Solution:
The pituitary gland
located just below the hypothalamus.
Hormones
secreted by anterior pituitary:
i.
Somatotropic Hormone (STH) / Somatotropin / Growth Hormone (GH): The
secretion of GH is high till puberty later its secretion becomes low. However,
it is continuously secreted throughout life for repair and replacement of body
tissue or cells.
Functions:
a. It stimulates the
growth of the body and the development of all tissues.
b. It accelerates
protein synthesis and cell division.
c. It stimulates the
release of growth hormone.
ii.
Thyroid Stimulating Hormone (TSH) / Thyrotropin:
Function:
It stimulates the
thyroid gland to produce the hormone thyroxine.
iii.
Adrenocorticotropic Hormone (ACTH) / Adrenocorticotropin:
a. It stimulates the
adrenal cortex to produce its hormones.
b. It maintains the
functioning of the adrenal cortex.
iv.
Prolactin / Luteotropin/ Mammotropin : The secretion of this
hormone is regulated by PIF (Prolactin inhibiting factor) of the hypothalamus.
Functions:
a. Activates the
growth of mammary glands during pregnancy (mammotropin).
b. Stimulates milk
production and secretion of milk (lactogenic) by the mammary gland after
childbirth.
v.
Gonadotropins:
a. Follicle
Stimulating Hormone (FSH): In males, it stimulates the development of seminiferous
tubules. In females, it stimulates the growth of ovarian follicles.
b. Luteinizing
hormone (LH): LH induces the ruptured follicles to develop into corpus
luteum and for the production of progesterone FSH and LH are responsible for
the stimulation of ovaries to produce estrogen.
c. ICSH: In
males, it stimulates the testes to produce the androgen called testosterone.
Testosterone is responsible for the development of secondary sexual characters.
Solution:
i. The
adrenal medulla is the inner region of the adrenal gland. It is the modified
sympathetic ganglion of the autonomic nervous system (ANS).
ii. The
chromaffin cells of the adrenal medulla secrete hormones rather than releasing
a neurotransmitter. These cells are innervated by sympathetic pre-ganglionic
neurons of the autonomous nervous system (ANS).
iii.
The autonomous nervous exerts direct control over the chromaffin
cells, thus the hormones – adrenaline and nor adrenaline can be released
quickly into the blood.
iv. The
impulses from the hypothalamus stimulate sympathetic pre-ganglionic neurons
which in turn stimulate the chromaffin cells to secrete adrenaline to
nor-adrenaline.
v. The
fight-or-flight response is initiated by nerve impulses from the hypothalamus
to the sympathetic nervous system, including the adrenal medulla. This response
rapidly increases circulation, promotes ATP production, and decreases
non-essential activities.
Thus,
the adrenal medulla and sympathetic nervous system function in a closely
integrated manner.
Solution:
Islets of Langerhans
are endocrine cells of the pancreas.
They are four types
of cells in Islets of Langerhans which have an endocrine role i.e. they secrete
hormones.
i.
Alpha cells (α cells): They constitute 20% of Islets of
Langerhans. They secrete hormone glucagon. Glucagon stimulates glycogenolysis
(the breakdown of glycogen) in the liver which causes hyperglycemia.
ii.
Beta cells (β cells): They constitute 70% of Islets of
Langerhans. They secrete insulin which stimulates glycogenesis (formation of
glycogen) in the liver and muscles. Insulin causes hypoglycemia by increasing
the uptake of glucose by cells.
iii.
Delta cells (δ cells): They constitute 10% of Islets of
Langerhans. These cells secrete somatostatin which inhibits the secretion of
insulin and glucagon. It also lowers gastric secretions, motility, and
absorption in the digestive tract. Somatostatin inhibits the release of growth
hormone.
iv.
PP cells or F cells: These cells secrete pancreatic polypeptide (PP) and inhibit the
release of pancreatic juice.
Solution:
Hypersecretion
of thyroid hormones: It is caused by an increase in the levels of thyroid hormones.
This increases metabolic rate, sensitivity, sweating, flushing, rapid
respiration, bulging of eyeballs, and affects various physiological activities.
Graves’ disease: Hyperthyroidism in adults results in this disorder. It is
characterised by protruding eyeballs, increased BMR, and weight loss. Increased
BMR produces a range of effects like increased heartbeat, increased B.P.,
higher body temperature, nervousness, irritability, and tremor of fingers.
Simple
goitre: It is iodine deficiency goitre. Iodine is required for the
synthesis of thyroid hormone and if there is a deficiency of iodine in the
diet, it causes enlargement of the thyroid gland leading to simple goitre. This
disease is common in hilly areas. Addition of iodine to table salt prevents
this disease. The size of the thyroid gland is increased but the total output
of thyroxine is decreased.
Solution:
Ovaries
secrete the following hormones:
i.
Progesterone: It is secreted by the corpus luteum of the ovary after ovulation.
It is essential for the thickening of the uterine endometrium, thus preparing
the uterus for implantation of the fertilized ovum. It is responsible for the
development of mammary glands during pregnancy. It inhibits uterine
contractions during pregnancy.
ii.
Oestrogen: It is secreted by developing follicles. Estradiol is the main
oestrogen. It is responsible for the development of secondary sexual characters
in females.
iii.
Relaxin: It is secreted by the corpus luteum of the ovary at the end of the
gestation period. It relaxes the cervix of the pregnant female and the
ligaments of the pelvic girdle to ease out the birth process.
iv.
Inhibin: It is
secreted by the corpus luteum. Inhibin inhibits FSH and GnRH production.
1.Explain the process of conduction of nerve impulses up to the
development of action potential.
Solution:
i. The nerve impulse is a
wave of bioelectrical or electrochemical disturbances passing along a neuron.
ii.
Neurons have a charged cellular membrane with a voltage that is different on
the outer and inner side of the membrane. The plasma membrane separates the
outer and inner solutions of different chemical compounds but having approximately
the same total number of ions.
iii. The external tissue
fluid has both Na+ and K+ but there is a predominance of Na+ and Cl-, while K+ is
predominant within the fibre or in the intracellular fluid. This condition of a
resting nerve is also called a polarised state.
iv. The polarized state of
a neuron is established by maintaining an excess of Na+ on the
outer side. On the inside, there is an excess of K+ along
with large negatively charged protein molecules and nucleic acid.
v. Some amount of Na+ and K+ always
leaks across the membrane. The Na+/K+ pump
actively maintains the ionic gradient across the resting membrane. The sodium
pump or Na-K allows the entry of K+ inside the membrane and
exit of Na+ .
vi. The difference in the
distribution of Na+ and K+ on the two sides of the membrane produces a
potential difference of – 50 to –100 millivolts (average is – 70 millivolts).
vii. The potential
difference seen in a resting nerve is thus called resting potential (–70
millivolts) and it is mainly due to differential permeability of the resting
membrane, which is much more permeable to K+ than to Na+. This
results in slightly more K+ diffusing out than Na+ moving inside and causing
a slight difference in polarity.
viii. Also, ions like
negatively charged proteins and nucleic acids inside the cell make the overall
charge negative on the inside and positive charge on the outside. The nerve
membrane not only has leakage channels but also has many gated channels for Na+ /K+. These
are also called voltage-gated channels. These channels enable the neuron to
change its membrane potential to active potential in response to stimuli. The
Na+ /K+ gated channels are separate so the transport of both these ions is
separately done. However, during resting potential, both these gates are closed
and the membrane resting potential is maintained.
ix. The resting potential
of the membrane is maintained unless the stimulus reaches the neuron. Any
change or disturbance to the membrane will cause Na+ to enter
into the membrane and lower the potential difference (lesser than –70
millivolts). Thus, the membrane becomes more permeable to Na+
x. During resting
potential, both gates are closed and resting potential is maintained. However, during
depolarization, the Na+ gates open and the K+ gates remain closed. This
causes Na+ to rush into the axon and bring about depolarisation (opposite of
polarity).
xi. The Extra Cellular
Fluid (ECF) becomes electronegative with respect to the inner membrane which
becomes electropositive. The value of action potential reaches +30 millivolts
to +60 millivolts. This triggers depolarization in the next part while it
itself starts going to repolarisation.
Solution:
3.Draw the neat labelled diagram of
Sectional view of the human eye.
Solution:
4.Draw the neat labelled diagram of L. S. of the human brain.
Solution:
5.Explain the role of the hypothalamus and pituitary as a coordinated unit in maintaining homeostasis?
Solution:i. The hypothalamus controls the secretory activity of the pituitary gland (anterior pituitary) by producing, releasing, and inhibiting hormones.ii. Anterior pituitary and intermediate lobes are connected to the hypothalamus through the hypophyseal portal system. Various hormones secreted by the hypothalamus reach the pituitary gland through the hypophyseal portal system.iii. The portal vein collects blood from various parts of the hypothalamus and opens into the anterior lobe of the pituitary. From the pituitary, the vein finally carries the blood into the superior vena cava. It helps in the feedback mechanism for hormonal control.iv. Also, a negative feedback mechanism takes place in the form of hormones released by the target glands to decrease the secretion of the pituitary gland.v. In such a negative feedback mechanism, the secretion of ACTH, TSH, and gonadotropins (FSH and LH) decreases when their target gland hormone levels rise.e.g. Adrenocorticotropic hormone (ACTH) stimulates the cortex of the adrenal gland to secrete glucocorticoids, mainly cortisol. In turn, an elevated blood level of cortisol decreases secretion of both corticotropin and corticotropin-releasing hormone (CRH) by suppressing the activity of the anterior pituitary corticotrophs and neurosecretory cells.
6.What is adenohypophysis? Name the
hormones secreted by it?
Solution:
Adenohypophysis: It
is an outgrowth from the roof of the buccal cavity. This outgrowth is called
Rathke’s pouch. It grows upwards towards the brain. It is the larger lobe of
the pituitary gland. It is a highly cellular and vascular part of the pituitary
gland. It contains various types of epitheloid secretory cells, acidophils,
basophils, chromatophores. It is further divided into three parts - Pars
distalis, pars tuberalis, and pars intermedia. Pars intermedia is poorly
developed in human beings. It is a small reduced part lying in the cleft
between the anterior and posterior lobe. It secretes Melanocyte Stimulating
Hormone (MSH) in some lower vertebrates. MSH stimulates the dispersion of
melanin granules in melanocytes and is responsible for skin pigmentation.
The
pituitary gland located just below the hypothalamus.
Hormones secreted by anterior pituitary:
i.
Somatotropic Hormone (STH) / Somatotropin / Growth Hormone (GH): The
secretion of GH is high till puberty later its secretion becomes low. However,
it is continuously secreted throughout life for repair and replacement of body
tissue or cells.
Functions:
a. It stimulates the
growth of the body and the development of all tissues.
b. It accelerates
protein synthesis and cell division.
c. It stimulates the
release of growth hormone.
ii.
Thyroid Stimulating Hormone (TSH) / Thyrotropin:
Function:
It stimulates the
thyroid gland to produce the hormone thyroxine.
iii.
Adrenocorticotropic Hormone (ACTH) / Adrenocorticotropin:
Functions:
a. It stimulates the
adrenal cortex to produce its hormones.
b. It maintains the
functioning of the adrenal cortex.
iv. Prolactin
/ Luteotropin/ Mammotropin: The secretion of this
hormone is regulated by PIF (Prolactin inhibiting factor) of the hypothalamus.
Functions:
a. Activates the
growth of mammary glands during pregnancy (mammotropin).
b. Stimulates milk
production and secretion of milk (lactogenic) by the mammary gland after
childbirth.
v.
Gonadotropins:
a. Follicle
Stimulating Hormone (FSH): In males, it stimulates the development of
seminiferous tubules. In females, it stimulates the growth of ovarian
follicles.
b. Luteinizing
hormone (LH): LH induces the ruptured follicles to develop into corpus
luteum and for the production of progesterone FSH and LH are responsible for
the stimulation of ovaries to produce estrogen.
c. ICSH: In males,
it stimulates the testes to produce the androgen called testosterone.
Testosterone is responsible for the development of secondary sexual characters.
7.Describe in brief, an account of
disorders of the adrenal gland.
Solution:
Disorders
of the adrenal gland:
i.
Addison’s disease: It is caused due to hypersecretion of glucocorticoids (hormone
secreted adrenal cortex). It is characterized by low blood sugar, low Na+, and
high K+ concentration in plasma increased loss of Na+ and water in urine. It
leads to weight loss, weakness, nausea, vomiting, and diarrhoea.
ii.
Cushing’s disease: It is caused due to Hyposecretion of mineralocorticoids (a hormone
secreted by the adrenal cortex) It leads to high blood sugar levels, excretion
of glucose in the urine, rise in Na+ level in the blood, high blood pressure,
obesity, and wasting of limb muscles.
8.Explain the action of steroid hormones and proteinous hormones.
Solution:
Hormones are released
in very minute quantities. They produce their effect on the target cells by
binding to hormone receptors. The hormone receptors are present on the cell
membrane (i.e. membrane receptors) or maybe intracellular receptors.
i.
Mode of hormone action through membrane receptors:
a. Hormones like
catecholamines, peptide, and polypeptide hormones are not lipid-soluble and
they cannot enter their target cells through the plasma membrane. These
non-steroid water-soluble hormones interact with surface receptors and initiate
metabolic activity.
b. Molecules of amino
acid derivatives, peptide hormones bind to specific receptor molecules located
on the plasma membrane.
c.
The hormone-receptor complex causes the release of an enzyme adenylate cyclase
from the receptor site. This enzyme forms cyclic AMP from ATP of the cell.
d. cAMP activates
enzymatic actions. The hormone acts as the first messenger and the cAMP acts as
the second messenger.
e. Some other
secondary messengers are Ca++, cGMP, and IP3 (Inositol triphosphate), etc.
ii.
Mode of action through intracellular receptors:
a. Steroid and
thyroid hormones are lipid-soluble and can easily pass through the plasma
membrane of the target cell into the cytoplasm.
b. In the cytoplasm,
they bind to specific intracellular receptors proteins forming a
hormone-receptor complex that enters the nucleus.
c. The
hormone-receptor complex binds to a specific regulatory site of DNA, in the
nucleus.
d. The activated
genes transcribe mRNA which directs protein synthesis and enzymes in the
cytoplasm.
e. The action of lipid-soluble hormones is slow but long-lasting,
9.Describe in brief an account of disorders of the thyroid.
Solution:
Disorders of the
thyroid gland are caused due to hypersecretion and hyposecretion of thyroid
hormones.
i.
Hypersecretion of thyroid hormones: It is caused by an increase
in the levels of thyroid hormones. This increases metabolic rate, sensitivity,
sweating, flushing, rapid respiration, bulging of eyeballs, and affects various
physiological activities.
Graves’
disease: Hyperthyroidism in adults results in this disorder. It is
characterised by protruding eyeballs, increased BMR, and weight loss. Increased
BMR produces a range of effects like increased heartbeat, increased B.P.,
higher body temperature, nervousness, irritability, and tremor of fingers.
ii.
Hyposecretion of thyroid hormone: It is caused by a deficiency
of thyroid hormones or removal of the thyroid gland (Thyroidectomy).
a.
Cretinism: It is caused due to deficiency of thyroid hormones in infants. A
cretin (individual suffering from cretinism) has reduced BMR and low oxidation.
They are short-statured because the skeleton fails to grow. They are mentally
retarded, show stunted growth and delayed puberty. They show dry skin, thick
tongue, prolonged neonatal jaundice, lethargy and constipation. This can be
treated by early administration of thyroid hormones.
b.
Myxoedema: It is caused due to the deficiency of thyroid hormones in adults.
It is characterised by a peculiar thickening and puffiness of skin and
subcutaneous tissue particularly of the face and extremities. The patient lacks
alertness, intelligence. The patient suffers from slow heart rate, low B.P.,
low body temperature (feels cold) and stunted sexual development.